AlN ceramics have excellent comprehensive properties, especially their outstanding thermal conductivity, and are therefore widely used in electronic and electrical开yun体育网 systems. Researchers have prepared dense AlN ceramics using different methods, achieving excellent thermal, electrical, mechanical, and optical properties.
Heat dissipation is a key consideration when developing devices. In theory, AlN has a thermal conductivity of up to 320 W · m-1 · K-1, making it an ideal heat dissipation material. The purity of AlN has a significant impact on its thermal conductivity. For every 1% increase in purity, its thermal conductivity can increase by 30%. This is because AlN relies on phonon conduction for heat transfer, and the scattering of phonons by impurities and defects can reduce the thermal conductivity of AlN ceramics. Especially oxygen atoms, which dissolve into the AlN lattice and replace nitrogen atoms to form aluminum vacancies, will cause strong vacancy defect scattering, leading to a decrease in thermal conductivity. Therefore, in order to obtain AlN ceramics with excellent thermal conductivity, the content of oxygen, impurities, and defects should be minimized as much as possible.
伸开剩余69%AlN ceramics and their performance parameters such as density and thermal conductivity are prepared by using different sintering aids and sintering methods to reduce sintering temperature and impurities. In addition, the in-plane thermal conductivity of AlN thin films developed by researchers at room temperature is approximately (260 ± 40) W · m-1 · K-1, which is one of the highest reported equivalent thickness thin film materials with the highest thermal conductivity.
For AlN ceramics, more attention and research are focused on their thermal conductivity. As a ceramic material with integrated structure and function, its dielectric properties should also receive sufficient attention. The energy transmission window of high-power microwave tubes should have characteristics such as low dielectric constant, low dielectric loss, and high thermal conductivity. AlN ceramics with high thermal conductivity and low loss perfectly meet this requirement.
AlN ceramics have a resistivity of 1014 at room temperature· cm， It has good electrical insulation properties and can be used as a ceramic packaging material for semiconductor surface passivation, semiconductor substrate materials, and electronic components. However, the resistance of AlN ceramics must be controlled according to their application scenarios in electronic devices. Usually, AlN ceramics with relatively high resistivity are used for electronic substrates and packaging materials, while AlN ceramics with relatively low resistivity are used for semiconductor devices.
AlN ceramics have excellent mechanical properties (high bending strength, modulus, and hardness), and the mechanical properties of AlN ceramics mainly depend on factors such as microstructure, phase composition, and density. The microstructure, especially the grain size and the type and number of grain boundaries, can have an impact on the mechanical properties of ceramics. Low density can reduce the stress area of ceramics and lower their mechanical properties开yun体育网, but attention should be paid to the synergistic effect of grain size and density. Grain growth is generally considered to be detrimental to mechanical strength, but sometimes it can reduce porosity (see Figure 2). Instead, improving density can enhance strength, and reducing the porosity and grain size of AlN ceramics can improve their mechanical performance indicators. In addition, AlN ceramics can also be used as optical ceramic materials.
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